To publish pages in child publications by selecting publishing of a master page you could employ the event system. Since you're on Tridion 2009 you will need to use the COM+ event system (can't use the new TOM.NET one).
The logic should be as follows:
You may want to put a publication metadata schema on the parent publication that will specify the IDs of the child publications that this cascaded publishing should work for (or create a configuration component). You will also need to specify which publication targets you'll want to publish to for the child publications.
In OnPublishPre (or Post) event use the TOM API to get Pages in the child publications and do page.Publish().
The advantage here is that content managers/publishers don't need to worry about having to go into the Advanced tab and select additional options.